tools: load direct kernel config from libvirt

tools: load direct kernel config from libvirt

When connected to libvirt we can validate that the guest configuration
has the kernel hashes property enabled, otherwise including the kernel
GUID table in our expected measurements is not likely to match the
actual measurement.

When running locally we can also automatically detect the kernel/initrd
paths, along with the cmdline string from the XML.

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>